1. Field of the Invention
The present invention relates to multilayer LC composite components, and more particularly, the present invention relates to multilayer LC composite components used in mobile communication apparatuses such as mobile phones and methods for adjusting the frequency characteristics of the multilayer LC composite components.
2. Description of the Related Art
A conventional multilayer LC composite component defining a multilayer LC filter is shown in FIG. 5. A multilayer LC composite component 1 in FIG. 5 includes ceramic sheets 2 to 9 having inductor via-holes 10a, 10b, 11a, 11b, 12a, and 12b formed therein, capacitor patterns 13 to 15, resonant capacitor patterns 16a, 16b, 17a, 17b, 18a, and 18b, coupling capacitor patterns 19 to 21, ground-side capacitor patterns 22 to 24, ground patterns 25 and 26, input and output lead patterns 27 and 28 disposed thereon.
The ceramic sheets 2 to 9 are stacked and a protecting ceramic sheet is disposed on the top and bottom of the stacked sheets. Then, the entire group of stacked sheets is integrally burned to constitute a multilayered body 50 shown in FIG. 6. An input terminal 51, an output terminal 52, and ground terminals G1 and G2 are disposed on the multilayered body 50. The input terminal 51 is connected to the input and output lead pattern 27, and the output terminal 52 is connected to the input and output lead pattern 28. The ground terminals G1 and G2 are connected to the ground patterns 25 and 26 and the ground-side capacitor patterns 22 to 24.
In the LC filter 1 having the above-described structure, the inductor via-holes 10a, 10b, 11a, 11b, 12a, and 12b are connected in the direction in which the ceramic sheets 2 to 9 are stacked to constitute pillar inductors L1, L2, and L3 having lengths d1. The resonant capacitor patterns 16a, 16b, 17a, 17b, 18a, and 18b are opposed to the ground pattern 25 and the ground-side capacitor patterns 22 to 24 via the ceramic sheets 2 to 4 to define resonant capacitors C1, C2, and C3. The capacitor patterns 13 to 15 are opposed to the coupling capacitor patterns 19 to 21 to define coupling capacitors Cs1, Cs2, and Cs3. In addition, connecting via-holes 41a to 41d, 42a to 42d, and 43a to 43d, are arranged to electrically connect the resonant capacitor patterns 16a, 16b, 17a, 17b, 18a, and 18b to the inductors L1, L2, and L3.
FIG. 7 is an electrically equivalent circuit diagram of the LC filter 1 constituted by the above-described arrangement. The pillar inductor L1 and the resonant capacitor C1 define an LC resonator Q1, the pillar inductor L2 and the resonant capacitor C2 define an LC resonator Q2, and the pillar inductor L3 and the resonant capacitor C3 define an LC resonator Q3. The LC resonators Q1 to Q3 are electrically connected to each other via the coupling capacitors Cs1 to Cs3 to constitute a three-stage band pass filter. Furthermore, mutual inductances M generated between the pillar inductors L1 to L3 and the coupling capacitors Cs1 to Cs3 define parallel traps to provide an attenuation pole at a frequency higher than the central frequency.
On the other hand, in the LC filter 1 having the above-described structure, one end of each of the inductors L1 to L3 is electrically connected to each of the capacitor patterns 13 to 15 to define the open-circuited end of each of the resonators Q1 to Q3. The other ends of the inductors L1 to L3 are electrically connected to the ground pattern 26 to define the short-circuited ends of the resonators Q1 to Q3. In addition, the input and output lead patterns 27 and 28 are always led from one end of each of the pillar inductors L1 and L3, that is, from the open-circuited ends of the resonators Q1 and Q3. As a result, in such a conventional LC filter, an attenuation pole that is formed at a frequency higher than the central frequency cannot be moved freely. Thus, the attenuation pole cannot be set near the central frequency.
In order to overcome the problems described above, preferred embodiments of the present invention provide a multilayer LC composite component that is arranged to allow for free and easy setting of an attenuation pole formed at a frequency higher than the central frequency. Also, preferred embodiments of the present invention provide a method for adjusting the frequency characteristics of the multilayer LC composite component.
According to a first preferred embodiment of the present invention, a multilayer composite component includes a plurality of insulation layers that are stacked to define a multilayered body, a plurality of inductors including via-holes connected in the direction in which the insulation layers are stacked, a plurality of capacitors including capacitor patterns, the inductors and the capacitors being arranged in the multilayered body to define a plurality of LC resonators, and one end of each of the inductors being electrically connected to the capacitor patterns of each of the capacitors defining the LC resonators, a ground pattern arranged one of the insulation layers to be electrically connected to the other ends of the inductors, and an input lead pattern and an output lead pattern arranged on one of the insulation layers to be electrically connected to midpoints of the inductors in the direction in which the insulation layers are stacked.
According to a second preferred embodiment of the present invention, a multilayer LC composite component includes a plurality of insulation layers including at least first to fifth layers arranged to define a multilayered body, a plurality of inductors and a plurality of capacitors disposed in the multilayered body to define a plurality of LC resonators, ground-side capacitor patterns arranged on the first insulation layer, hot-side capacitor patterns arranged on the second insulation layer to define the capacitors of the LC resonators, the hot-side capacitor patterns being opposed to the ground-side capacitor patterns, input and output lead patterns arranged on the third insulation layer, first inductor-via-holes formed in the third insulation layer and connected to the input and output lead patterns, second inductor-via-holes formed in the fourth insulation layer, and a ground pattern arranged on the fifth insulation layer, wherein the first to fifth insulation layers are stacked and then the first and second inductor via-holes are connected in the direction in which the insulation layers are stacked to define the inductors, one end of each inductor being electrically connected to the hot-side capacitor patterns of each of the capacitors defining the LC resonators and the other ends of the inductors being electrically connected to the ground pattern arranged on the fifth insulation layer, and the input and output lead patterns arranged on the third insulation layer being electrically connected to midpoints of the inductors in the direction in which the insulation layers are stacked.
In addition, preferably, a distance between the ground pattern and each of positions connecting the input and output lead patterns to the inductors is within a range of between about 200 xcexcm and about 700 xcexcm in the direction in which the insulation layers are stacked. With this arrangement, desired input and output impedances such as approximately 50xcexa9, 70xcexa9, and 75xcexa9 Q can be obtained.
According to a third preferred embodiment of the present invention, a method for adjusting the frequency characteristics of a multilayer LC composite component in which insulation layers are stacked to define a multilayered body inside which a plurality of inductors and a plurality of capacitors are disposed to constitute a plurality of LC resonators, includes the steps of forming the plurality of inductors by forming via-holes connected in the direction in which the insulation layers are stacked, electrically connecting one end of each of the inductors to capacitor patterns of each of the capacitors defining the LC resonators and electrically connecting the other ends of the inductors to a ground pattern arranged on one of the insulation layers, and changing positions at which input and output lead patterns arranged on one of the insulation layers are connected to the inductors in the direction in which the insulation layers are stacked to adjust the frequency characteristics.
In this method, the input and output lead patterns are electrically connected to the midpoints of the inductors in the direction in which the insulation layers are stacked. This arrangement permits an attenuation pole formed at a frequency higher than the central frequency to come close to the central frequency. In other words, by shortening the distance between the ground pattern and each of the positions electrically connecting the input and output lead patterns to the inductors, the inductances of parallel trap circuits are increased, whereby the attenuation pole comes close to the central frequency. As a result, the frequency characteristics of the multilayer LC composite component can be easily and accurately adjusted.
Other features, elements, characteristics, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments of the present invention with reference to the attached drawings.